Here's how the name breaks down: Natgeosocus is the name of the new genus. Sorini is the new species, a nod to Romanian paleoichthyologist Dorin-Sorin Baciu, who extricated the skeleton from the clay that encased it.

Finding the fish was "a great surprise for me," because the only relative of the new genus lives in Denmark and is 20 million years older, said Bannikov, of the Russian Academy of Sciences' Paleontological Institute, in an email.

The species likely swam alongside many well-known modern fish such as herring, cod, and mackerel, Bannikov said, as well as other species in its own family, Palaeocentrotidae, which is now extinct. (A family is the taxonomic ranking above genus.)

Members of Palaeocentrotidae were not only rare, but had "extraordinarily peculiar" physical characteristics, he added.